And in las vegas tonight, a stunning headline. Just how did a 9-year-old boy slip past several layers of airport security to hop on a plane to vegas? No tict, nothing. Abc's aditi roy tonight on how the airline and the airport are explaining this. Reporter: A bold breach at the minneapolis-st. Paul international airport last week. The surprising culprit? A 9-year-old boy. He must know something about the system or simply good luck. Reporter: Airport officials say the 9-year-old managed to fly to las vegas without a ticket or boarding pass. And went through three levels of security. The tsa agent, the metal detector and the gate agent. The delta flight took off. The crew became suspicious since he was not on their list of children flying alone. After landing in las vegas, the boy was taken into protective custody. Authorities believe he is a runaway. I think it's probably easier for a 9-year-old, because people assume 9-year-olds are being escorted, they assume a 9-year-old hasn't got the audacity to do it. Reporter: In a statement, delta says it is investigating the inls incident. After beating the system, the 9-year-old is expected to be sent back to minneapolis. David? Aditi, thank you.

This transcript has been automatically generated and may not be 100% accurate.

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